I set up a Xonotic Server on DigitalOcean a while back. It hasn't seen much activity though. So I'm here to promote my server.
Ivan's Vanilla+NewToys is a Xonotic Autobuild server. There's only one server, hosted in San Francisco, but it supports the following gamemodes: deathmatch, team deathmatch, capture the flag, keepaway, clan arena, assault.
New_Toys is enabled, so you can use the Rifle and Minelayer
By default an "Unhuman" bot will join along with the player. The diffficulty and amount can be customized by votes.
All official maps are available. Enjoy playing Xonotic on my server - all are welcome

Xonotic documentation contributor. Owner of the itch.io page for Xonotic.

Thank you for setting up a server! I've found the best way to have people play on your server is...
Hop onto your own server and start playing for a while. Most people are attracted to servers that have more than 0 people on them.